1. Field of the Invention
The present invention relates to a power supply terminal which is connected to a solenoid coil of a magnet switch mounted in a starter and connectable to an external circuit of the starter. More particularly, the present invention relates to a power supply terminal which has an overheating suppressing mechanism or which is adapted for use in a single axis-type starter.
2. Description of Related Art
It is disclosed in Japanese Patent Publication (JP-B2) No. 6-74778 to detect, by a temperature sensor provided adjacently to a solenoid coil of a magnet switch, the excessive temperature rise of the solenoid coil and to interrupt electric power supply to a motor. In this magnet switch, a normally-closed bimetal and a temperature fusible link are shown exemplarily as the temperature sensor. As the temperature sensor is provided in contact with the solenoid coil of the magnet switch, an energization circuit can be interrupted in response to the excessive temperature rise of the solenoid coil but not in response to the temperature of a solenoid coil terminal itself.
Because large electric current flows to the power supply terminal of the magnet switch for a starter so that the solenoid coil is energized sufficiently to attract a plunger, conduction failure of the terminal leads to the temperature rise. The conduction failure occurs when the connection of the terminal with an external plug is loosened by vibrations, when the contact surface of the terminal is stained by water or dust or when the electric resistance of the contact surface or a connecting portion with an electrical lead wire is increased by rusting. Further, it often occurs that the terminal is connected too loosely or the external plug is improperly inserted for engagement with the terminal.
When the conduction failure occurs due to some of those reasons and the electric resistance increases, abnormal temperature rise occurs at the time of energization of the solenoid coil. Despite this fact, because the temperature sensor is provided apart from the terminal in the conventional magnet switch, the excessive temperature rise of the terminal itself cannot be detected and the above-described drawback cannot be obviated.
A single axis-type starter is proposed by Japanese Utility Model Publication Laid-open (JP-U) No. 1-179176. This single axis type starter has a speed reduction mechanism, a motor and a magnet switch which are all disposed axially in line. The reduction mechanism has a pinion disposed engageably with an engine ring gear through an output shaft. The motor is adjacently disposed at the axially rear side of the reduction mechanism to drive the reduction mechanism by a motor rotary shaft extended in the same direction as the output shaft. The magnet switch is adjacently disposed at the axially rear side of the motor to control electric power supply to the motor. The magnet switch is surrounded by an end cover having an opening facing an outer rear casing end of the motor.
As the starter radial length can be shortened by a distance the magnet switch is disposed at the rear side of the motor in the single axis-type starter, it is advantageous that it may be easily mounted, for instance, at the side of an engine block. The starter axial length is likely to be necessarily lengthened by the shortening of the radial length. This will cause some difficulty in assuring a required space for the starter and other equipment at the axially rear side of the starter in an engine compartment.
In the single axis-type starter, in particular, a power supply terminal for a solenoid coil of the magnet switch protrudes from the rear end surface of the end cover. Therefore, in the case that the rear side space of the magnet switch is reduced by the lengthening of the starter axial length, it becomes difficult to connect and disconnect an electric cable to and from the power supply terminal of the solenoid coil.
Further, the power supply terminal of the solenoid coil is usually narrow and soft. Therefore, the terminal may be damaged or bent in the case of dropping or hitting other equipment at the time of starter mounting work or cable connecting/disconnecting work. This makes it difficult to connect it with an external cable.